The flower spikes of bottlebrushes form in spring and summer and are made up of a number of individual flowers. The pollen of the flower forms on the tip of a long coloured stalk called a filament. It is these filaments which give the flower spike its colour and distinctive 'bottlebrush' shape. The filaments are usually yellow or red, sometimes the pollen also adds a bright yellow flush to the flower spikes. Each flower produces a small woody fruit containing hundreds of tiny seeds. These fruits form in clusters along the stem, and are usually held on the plant for many years. The seeds are usually not released from the fruits for several years, but in some species the fruits open after about a year. Fire also stimulates the opening of the fruits in some bottlebrushes